Rosemary Beetle
Pest · Commonly affects: Rosemary, Lavender, Sage, Thyme, Oregano, Marjoram
Rosemary beetle is a colourful but unwelcome leaf beetle that feeds on aromatic Mediterranean herbs. It has become established in many UK gardens and is most often found from autumn into spring, when rosemary and lavender are still valued for structure and fragrance. Light damage is tolerable, but unchecked colonies can spoil shoots and weaken container plants.
How to identify it
Adults are oval beetles about 6-8 mm long, with metallic green and purple longitudinal stripes. Their soft-bodied larvae are greyish with darker markings and are often found among the same foliage. Search rosemary, lavender, sage and thyme carefully, especially the growing tips and sheltered inner stems. Look for chewed, ragged leaves, dark droppings and clusters of eggs fixed to the underside of leaves. Adults may drop when disturbed.
Damage
Adults and larvae nibble leaves and tender shoots, producing notches, ragged foliage and thinning growth. Severe feeding can reduce the supply of aromatic leaves for cooking and make shrubs look tired before flowering. Young or pot-grown herbs are most likely to suffer, particularly if they are already stressed by poor drainage, drought or winter cold.
Prevention
Grow herbs in free-draining soil and give container plants enough room, light and watering to remain vigorous. Inspect plants when bringing them home from a garden centre and before moving pots into sheltered positions for winter. Avoid overcrowding, which hides pests in dense growth. Prune lightly after flowering where suitable to keep shrubs open, and encourage birds and predatory insects with mixed planting nearby.
How to manage it
Pick off adults, larvae and egg clusters by hand during regular inspections, dropping them into soapy water. Pay close attention to new growth from autumn through spring, when numbers can build quietly. Prune out heavily infested shoot tips and dispose of them in household waste if larvae are present. Recheck neighbouring herbs because beetles readily move between closely planted rosemary, lavender, sage and thyme.
Rosemary Beetle: frequently asked questions
How do I identify rosemary beetle?
Adults are oval beetles about 6-8 mm long, with metallic green and purple longitudinal stripes.
How do I prevent rosemary beetle?
Grow herbs in free-draining soil and give container plants enough room, light and watering to remain vigorous.
How do I get rid of rosemary beetle?
Pick off adults, larvae and egg clusters by hand during regular inspections, dropping them into soapy water.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.